---
title: Goose harness
description: >-
  The Goose harness runs Goose in the sandbox on a Gemini API key and records
  its events.
---
> ## Documentation Index
> Fetch the complete documentation index at: https://docs.reeval.ai/llms.txt
> Use this file to discover all available pages before exploring further.

`goose()` runs Goose (`goose acp`) in the sandbox. For more information about the sandbox, see [Choose a sandbox](/configuration/sandboxes).

## `GOOGLE_GENERATIVE_AI_API_KEY`

`goose()` reads `GOOGLE_GENERATIVE_AI_API_KEY` from the environment or the `.env.local` file. A run exits with code 2 when the variable is unset, or when the value contains whitespace or a line break.

Goose reads that value as `GOOGLE_API_KEY`. The gateway brokers the key in the `x-goog-api-key` header on `POST /v1beta/models/<model>:streamGenerateContent` and `GET /v1beta/models` at `generativelanguage.googleapis.com`. A restricted egress policy allows `generativelanguage.googleapis.com`.

When the API rejects the key, the attempt error begins with `The API rejected GOOGLE_GENERATIVE_AI_API_KEY: set a valid key in the environment or .env.local`.

For more information about keeping API keys on the host, see [Keep API keys on the host](/configuration/environments/secrets#keep-api-keys-on-the-host).

For more information about the variable, see [`GOOGLE_GENERATIVE_AI_API_KEY`](/reference/environment-variables#googlegenerativeaiapikey).

Goose requests `models.dev` in every session to refresh its model catalog, and no setting turns that request off. A restricted egress policy refuses `models.dev` and records it on `egress.expectedBlocked`.

For more information about blocked requests, see [Read blocked requests](/configuration/environments/egress#read-blocked-requests).

## `goose()`

`goose()` is exported from `{{ pkg }}/harness`. The following configuration passes it as the `harness` option:

```ts title="reeval.config.ts"
import { defineConfig } from '{{ pkg }}'
import { goose } from '{{ pkg }}/harness'

export default defineConfig({
  harness: goose({
    model: 'gemini-3.8-flash',
    effort: 'high',
  }),
})
```

`model` is required. For what each field takes, see [Harness factory options](/reference/options#harness-factory-options).



In the sandbox, Goose runs with a private home, with telemetry, the keyring, and session naming off.

For more information about model ids and effort values, see [Set the agent's model](/configuration/agents/model). For rules, skills, MCP servers, usage, served models, and web events, see [Harness behavior](/reference/options#harness-behavior).

## `plugins`

reeval adds each plugin's skills to the home skills directory and writes its MCP servers as enabled extensions in `config.yaml`.

[//]: # (generated:harness-plugins:goose)

- Takes `skills` and `mcp`, and refuses a plugin that keeps `agents`, `commands`, `hooks` and `rules`: narrow it with `only`, or leave it out of the cell.

[//]: # (/generated:harness-plugins:goose)

For more information about plugins, see [Environment helpers reference](/reference/environment-helpers#pluginlocal).